This invention relates to a circuit arrangement for operating a lamp comprising                input terminals for connection to the poles of a supply voltage source,        a circuit part I coupled to the input terminals for generating a current through the lamp from a supply voltage delivered by the, supply voltage source, and        a circuit part II coupled to the circuit part I for controlling the power consumed by the lamp, and comprising a circuit part IIa for generating a first signal that represents a desired value of the power consumed by the lamp.        
Such a circuit arrangement is known from U.S. Pat. No. 5,111,118. In the known circuit arrangement the circuit part II makes sure that the power consumed by the lamp is hardly influenced by a change in operational parameters such as the amplitude of the supply voltage. In case the amplitude of the supply voltage decreases the amplitude of the current drawn from supply voltage has to increase. However, if the amplitude of this supply current increases too much this increase can lead to damage to components of circuit part I. More in particular, in case the circuit part I comprises a DC-DC-converter, such as an up-converter, operating in the transition mode, an increase of the average current drawn from the supply voltage source corresponds to an increase the maximal amplitude of the current drawn from the supply voltage source that is twice as big. In this latter case damage to components can even happen when the decrease in the amplitude of the supply voltage is relatively small.